Blue Light Excites Retinal, Intercepts Cellular Signaling in the Eye

BioPhotonicsSep 2018
An optical chemistry research study has shown how blue light from digital devices and the sun can cause the death of retinal molecules, increasing potential for age-related macular degeneration.

Photoreceptor chromophore 11-cis retinal (11CR) and the photoproduct all-trans retinal (ATR) are present in the retina and interact with the visual cells. Using live-cell imaging and optogenetic signaling control, researchers at the University of Toledo showed that blue-light-excited ATR and 11CR can irreversibly change phosphatidylinositol 4,5-bisphosphate (PIP2) and disrupt its function. The change in PIP2 was followed by excessive cell shape change and cell death.

Ajith Karunarathne examined toxic oxygen generation by retinal during blue light exposure. Courtesy of Dan Miller, The University of Toledo.Researchers introduced retinal molecules to other cell types in the body, such as cancer cells, heart cells, and neurons. When exposed to blue light, these cell types died as a result of the combination with retinal. Blue light alone had no effect on cells. Retinal alone, without blue light, had no effect. No activity was incited by green, yellow, or red light.

The research suggests that retinal exerts light sensitivity to both photoreceptor and nonphotoreceptor cells.

“It’s no secret that blue light harms our vision by damaging the eye’s retina,” said professor Ajith Karunarathne. "Our experiments explain how this happens, and we hope this leads to therapies that slow macular degeneration, such as a new kind of eye drop."

Researchers also found that alpha tocopherol, a vitamin E derivative, can stop cells from dying from exposure to blue light and retinal combined.

The researchers are currently measuring light coming from television, cellphone, and tablet screens to better understand how the cells in the eye respond to everyday blue-light exposure.

To protect the eyes from blue light, Karunarathne suggests wearing sunglasses that can filter both UV and blue light when outside, and to avoid looking at cellphones or tablets in the dark.

“Some cellphone companies are adding blue-light filters to the screens, and I think that is a good idea,” said professor John Payton.

Photoreceptor cells do not regenerate in the eye, the researchers said.

“Every year, more than two million new cases of age-related macular degeneration are reported in the United States,” Karunarathne said.

“By learning more about the mechanisms of blindness in search of a method to intercept toxic reactions caused by the combination of retinal and blue light, we hope to find a way to protect the vision of children growing up in a high-tech world.”

A discipline that combines optics and genetics to enable the use of light to stimulate and control cells in living tissue, typically neurons, which have been genetically modified to respond to light. Only the cells that have been modified to include light-sensitive proteins will be under control of the light. The ability to selectively target cells gives researchers precise control.
Using light to control the excitation, inhibition and signaling pathways of specific cells or groups of...